Process for making copper-iron powder



PROCESS FOR MAKENG COPPER-IRON POWDER Marion Ernest Graham, Parma, andWilliam A. Reed,

West Richiield, ()liio, assignors to Republic Steel Corporation,Cleveland, ()hio, a corporation of New Jersey No Drawing. ApplicationDecember 29, 1953, Serial No. 401,063

5 Claims. (Cl. 75-05) This invention relates to a process for makingarticles consisting essentially of copper and iron, having a hightensile strength and high density and more particularly to a process formaking copper-iron powder from which such articles may be fabricated bypowder metallurgy methods.

This case is related to the co pending application of Marion ErnestGraham and William A. Reed entitled Process for Making Copper-IronPowder, Serial No. 401,064, filed December 29, 1953. This co-pendingapplication discloses a method for making copper-iron powder by thereduction of iron oxide in the presence of certain reducible coppercompounds or metallic copper and particularly in the presence of gaseoushydrogen chloride which must be supplied from an external source.

The line of division between the invention of that application and thepresent invention resides in the fact that the present invention'relatesto the reduction of certain iron and/or copper compounds by hydrogen.The supplying of gaseous hydrogen chloride from a separate source duringreduction is not a necessary feature of the present invention. Saidco-pending application relates to the production of copper-iron powderby a reduction step effective on iron oxide plus a source of copper byhydrogen wherein HCl gas must be supplied from an external or separatesource during the reduction.

High strength and high density articles consisting essentially of copperand iron have found numerous industrial applications, notably in themanufacture of turbine blades and other parts subjected to wear andrequiring quite high strength. In the past, such parts have beenproduced by such methods as infiltration of molten copper into ironparts previously prepared by powder metallurgy methods and the coiningof parts made from mixtures of copper and iron powders. While suchmethods may be ettective in producing articles having a high tensilestrength, they are objectionable in that they involve substantially morecomplexity and expense of operation than do powder metallurgy processes.

it is an object of this invention, therefore, to provide a process formaking articles of high tensile strength consisting essentially ofcopper and iron that utilizes the relatively simple methods of powdermetallurgy.

It is a further object of the invention to provide a process for makingcopper-iron powder, which is capable of being formed into articleshaving a high tensile strength and high density by pressing andsintering and without the necessity of infiltration, coining or similaroperations.

ther objects of the invention will be in part apparent and in partpointed out by the subsequent description.

The process of the invention may be carried out by reducing one of thehydrogen-reducible oxides of copper such as CuO or 0120 or one of thehydrogen-reducible chlorides of copper such as CuClz or CuCl in intimateadmixture with iron powder of either one or both of two special types,i. e. iron powder that has been made either nited rates Patent by thehydrogen reduction of iron chloride or by the reduction of iron oxide bya mixture of hydrogen and hydrogen chloride. This reduction is carriedout by hydrogen or by a reducing gas containing hydrogen as itsessential active ingredient. It has been found that in order to producea copper-iron product having the desired physical properties inaccordance with the present invention, an actual chemical reduction ofthe copper compound must take place while it is in intimate contact withthe special type iron powder as aforesaid. Furthermore, the metalliciron ingredient of the starting material must have been made either bythe reduction of iron chloride by hydrogen or by the reduction of ironoxide by a mixture of hydrogen and hydrogen'chloride. cases, it may bedesirable to produce a metal powder having some predetermined carboncontent. To this end it may be necessary to add a small amount of carbon(e. g. about 1%) to the starting mixture.

After the ingredients of the starting material, selected in accordancewith the principle outlined above, have been mixed together in theproportions that will result in the desired ratio of iron to copper inthe reduced prod uct, the starting material is introduced into areaction zone and there contacted with a reducing gas containinghydrogen. The solid starting material and the reducing gas are bothmaintained at an elevated temperature in the range of about 1000 F. toabout 1800 F. and contact between them is continued until the reductionof the hydrogen-reducible copper compound has been substantiallycompleted. The resultant material is then cooled and, in the event thatit be in a massive or semi-sintered condition, is comminuted to powder.This copper-iron powder may then be pressed to a self-sustaining mass ofpredetermined size and shape, which is subsequently sintered in asuitable non-oxidizing atmosphere usually at a temperature of about 2000F. The physical properties of the resulting article will be in partdependent upon the ratio of iron to copper contained therein, thepressure at which it was molded, the sintering temperature and otherfactors, but in all cases the product of the present invention will havea higher tensile strength than conventional copper-iron parts of thesame chemical composition which have been pressed and sintered undersimilar conditions respectively. In many instances, the tensile strengthof articles made in accordance with the process of the present inventionwill exceed 100,000 pounds per square inch.

Summarizing the present invention, copper-iron powder suitable for usein powder metallurgy for forming articles having high tensile strengthand high density is produced by introducing into a reaction zone astarting material, the essential active ingredients of which consist of:metallic iron powder, in at least one form selected from the groupconsisting of (a) metallic iron which has been reduced from iron oxideby a reducing gas containing hydrogen chloride, and (b) metallic ironwhich has been reduced from iron chloride by hydrogen, and copper, in atleast one form selected from the group consisting of (a) the chloridesof copper, and (b) the oxides of copper; and then contacting saidstarting material with a reducing gas containing hydrogen as anessential active reducing ingredient under such conditions oftemperature and for such a time as to reduce the hydrogen-reduciblecopper compound to metallic copper.

Since it is an object of the present invention to produce a copper-ironpowder, the ingredients of the starting ma terial are preferablyprovided in finely-divided form. This further facilitates thoroughmixing of the ingredients of the starting material, which is necessaryto insure the production of a chemically uniform and homogeneousmaterial.

The ingredients used for the starting material must in- In some elude atleast one copper-containing ingredient and at least one iron-containingingredient. The eo pefleentainin ingredient is one or more materialsselected from the group consisting of the hydrogen-reducible oxides ofcopper, i. e., CuO and CuzO and the hydrogen reducible chlorides ofcopper, i. e., CuClz and CuCl. All that is required is that the coppercompound shall have a particle size sufficiently small to insure the,production, of; a substantially homogeneous mixture as the startingmaterial. The same consideration is controlling with regard to theparticle size of the other ingredient of the starting material. a a 7 Itis immaterial, insofar as the operation ofthepresent invention isconcerned, whether the copper compound ingredient be in thecupric orcuprous state or a: mixture ofboth. It is believed thatwhen cupricoxid'e for example, is reacted with a suitable reducing agent, it isinitially converted to cuprous oxide as an intermediate stage in thereduction to metallic copper. It is believed that an analogous processtakes placefinthe reduction of.

cupric chloride, i. e., that cuprous chloriide is formed as anintermediate product. Whether these theoriesbe accurate or not, it hasbeen found that the cupric and cuprous forms of both the oxide and; thechloride, are equally effective and as such are the equivalents of oneanother for the purposes of the present invention. They are bothintended to be included in the terms icopperoxide and copper chloride,respectively, as those terms are used herein and in the appendediclaims,

It is a), be further understood that the terms copperv oxide? and copperchloride as used herein, are meant to include those copper compoundswhich decompose easily under the influence of heat to form oxides orchlorides. alates, formates and similar organic salts, which quicklyform oxides when heated, and are so converted in the reaction zonebefore reduction actually begins. These compounds may, therefore, beconsidered the chemical equivalent of copper oxide for the purposes ofthe present invention. Similarly, hydrated chlorides of copper such asCuC12-2H2O which lose their water of hydration at elevated temperaturesmay be used as the copper-containing ingredient. I a p The one or moreiron-containing ingredient ort ingretdients of the starting material is.or are selected from a groupsomewhat more circumscribed than that fromwhich the copper-containing material is chosen. For want of a betterterm, this iron may be referred to a s chloride iron because its processof production involves. the pres ence of a chloride, and in theory it isbelieved to be derived, either directly or indirectly, from or toinvolve the reduction of iron chloride. Thus, iron powder made by thehydrogen reduction thereof of iron chlorideis among the ironcontaining.materials that may be used as a start-Y he ing material inpracticing the present inv ntiOn. other possible iron-supplyingingredient is metallic iron thathasj been made by the reduction of. ironoxide with a mixture of hydrogen and a substantial amount oil hydrogenchloride as taught, for example, in the Crowley application, SerialNo..375,927, filed August 24,. 1953.

Experience and research tests have shown that iron powder of this typediffers substantially as to its physical properties and metallurgicalstructure from iron powder made by the reductionof iron oxide with purehydrogen or other reducing agent free of substantialamounts of the factthat during the reduction process; the iron; oxide is converted at leastmomentarily to ferrous: chloride,

which is then reduced to metallic iron. This theory tends;

Examples of such compounds are acetates, ox-

1-101. It is believed that this difference may be; duet-to,

4 established empirically regardless of the theoretical reasonstherefor.

It is essential to the production of the high strength articles, whichis an object of this invention, that the ingredients of the startingmaterial be selected in such a way that at least one of them (ahydrogen-reducible copper compound) is reduced in the presence of theother or others (a special form of iron powder). Thus, metallic copperand metallic iron (even iron made in the presence (senor-or by reducingiron chloride) and when no hydrogndeducible material is present, thewhole then treated in hydrogen, did not produce the desired material.Subsequentexamples willillustrate that copper-iron powder made in thisway is definitely inferior as to its tensile strength to copper-ironpowder made in accordance with the teachings of the invention. The factthat a chemical reduction reaction takes place while the ingredients aremixed together appears to be necessary for the production of the-novelcopper-iron powder of thepresent invention, which iscapableof-pr'oducin'g sintered bodies of unusually. hightensile: strength.Thereason for this novel requirement'of; the present invention is notfully understood;v

After the ingredients of the starting material have been selected-inaccordance with the principles outlined above, they;are proportionedsoas to result ina reduced powder having thedesired ratio of copper toiron andare thoroughlyv mixed; In order that thorough mixing take place,it is;.desi rable;that the starting, ingredients be supplied in the formof powdenqand preferably, as finely divided as isiconvenient.In-practiceit hasbeen found that excellent is, obtained by the. use ofmesh starting materials,

The. mixedingredients may then be placed in a suitable container, suchas a, metal boat or pan, and introduced into; a: reaction zone, wherein"the hydrogen-reducible copper constituent of'the starting materialisreduced. In.

order to insure, maximumyield based on the amount of raw; materialpsed,it. is. necessary: that the chemical reaction be carried to substantial,completion. By this it is meant thatthe; copper of thehydrogen-reducible copper compoundbe-reduced to an oxidation state ofzero. This phrase; as; usedin this description, and the appended claims,isqmcantto embrace boththe production of either a physicalmixture ofelementalmetallic powders or the production of; some alloy, of copperand iron alone: or which may bemixedtwith, a simple mixture of copperand iron. Irr-any case the; metallicconstituents-are pres.- entinanpxidation state of zeroas opposed to the positive xi ation tate n chppe rp y v ingredient wasintroduced in the starting material as copperchloride; etc.

The QQlldltlQllSgOf reduction are notcriticalto the succes of ithe-process exceptthat they mustbe-sufiicient as;

sinterdproduqt,.Which willbe difficult to grind. This" condition is tobe avoided, since one .of the objects of-the presentv invention is theproduction'of pulverulent material whichmay be;used;in powder metallurgyprocesses. It has ,been'found thattemperatures up to. about1800 F.

will.res,ultvin: the production of materialwhich is quite frangible and:thus: may. be, comminuted to powder without unduje ,trouble or expense.

After -.the -reductionhas. been completed, the reduced powder iscooled1in-a non-oxidizing atmosphere toabout 200 F. tin-less;Theresultant:mass -is then comminuted to; powder; which; iS-;,th en used. in various powder;- metallur'gpprogesses,according-to";standard-practice;

The process of the present invention is further illustrated by thefollowing examples, which are not intended as narrowly limiting upon thescope of the present invention.

Example I Finely divided metallic iron, made by the hydrogen reductionof ferrous chloride, was mixed with cupric chloride (CuClz) and treatedwith hydrogen supplied at the rate of 2000 cubic centimeters per minuteand a temperature of 1200 F. for 3 hours. This was done by blending thefinely divided metallic iron in a dry state with the copper cloride, soas to obtain a reduced material including the metals iron and copper inthe weight ratio of about 85% iron and about 15% copper. The mixture ofiron and copper chloride was spread on a tray to a depth of about 4 inchand the tray placed in an electrically heated mufile furnace. Dryhydrogen Was passed through the furnace over the surface of the mixtureat the rate of 2,000 cubic centimeters per minute throughout thereduction. The temperature of the contents of the furnace was maintainedat about 1200 F. for 3 hours. The sealed inner tube of the furnace wasthen removed from the heating muffle and the contents allowed to cool toa temperature below 200 F. The completely reduced copper-iron productwhich had formed into a semi-sintered,

but easily frangible, cake was then ground to a particle size of about100 mesh. The resulting powder was found by analysis to contain 15.83%copper and the ballance, principally iron. This powder was mixed with 1%zinc stearate as a lubricant, pressed at 50,000 p. s. i. to form astandard test bar, which was then sintered in hydrogen at 2000 F. forone hour. The resulting piece had a tensile strength of 113,000 p. s. i.In addition to copper and iron this powder also contained about 0.24%carbon. It is believed that the unusually high strength obtained in thisinstance may have been due, in part, to the presence of this smallamount of carbon. This example thus also demonstrates that the presenceof a small amount of carbon in the powder is not deleterious insofar astensile strength is concerned.

Example II Copper-iron powder was prepared under the same conditions asthose described in Example I, except that cuprous oxide was used insteadof cuprous chloride. The powder thus prepared contained 14.92% copperand 0.074% carbon. A pressed and sintered test piece prepared from thispowder by the standard procedure above set forth had a tensile strengthof 82,400 p. s. i.

Example III Metallic iron prepared by the reduction of iron oxide with amixture of hydrogen and hydrogen chloride may be used as a substitutefor reduced ferrous chloride, although the tensile strengths obtainableunder these circumstances are not as high as those resulting from theuse of ferrous chloride or reduced ferrous chloride. For example -325mesh iron powder prepared by the reduction of iron oxide (FezOa) at 1400F. with a mixture of hydrogen and hydrogen chloride was mixed withcuprous oxide (CuzO) and treated with hydrogen at 1200 F. to reduce thecopper oxide. The resulting copper-iron powder, containing 14.32%copper, was pressed and sintered according to the standard procedureabove outlined and yielded a piece having a tensile strength of 62,200p. s. i. While this powder does not yield pieces having as high atensile strength as those set forth in the previous examples, itsstrength is still almost double that obtained using prior art practicesand starting materials. Thus,

when copper oxide and commercial iron powder, made by the comminution ofsponge iron and without the use of hydrogen chloride, were mixed in thesame proportion given in the first portion of this example and reducedwith hydrogen at 1200 F., and this powder pressed and sintered inaccordance with the standard procedure, there was produced a piecehaving a tensile strength of only 32,000 p. s. i. A comparison of thesetwo values illustrates the unexpected and valuable results obtained inaccordance with the present invention by providing the iron in one ofthe forms set forth hereinabove. Merely reducing any copper compound inthe presence of any metallic iron is ineffective to produce the productof the present invention.

Example IV Metallic iron reduced with a mixture of hydrogen and hydrogenchloride under the conditions described in Example III was reduced withcupn'c chloride by hydrogen at 1100 F. to a powder containing 15.25%copper. A piece pressed and sintered from this powder in accordance withthe standard procedure above set forth had a tensile strength of 65,700p. s. i.

Example V Example III illustrated that the mere reduction of a coppercompound in the presence of metallic iron not derived in some mannerfrom a chloride source and/or in the presence of HCl does not producethe desired copperiron powder of the present invention. This exampleillustrates that the mere presence of metallic iron of the proper typeaccording to the present invention but without the presence of ahydrogen-reducible copper compound is similarly undesirable and is notto be considered as included in the present invention.

Thus, when a reduced metallic iron made by the hydrogen reduction offerrous chloride is mixed with metallic copper, both metals when mixedbeing in finely divided form, and mixed in the proportions of 15% copperand iron, then pressed and sintered according to the standard procedureabove set forth, a piece having a tensile strength of only 48,200 p. s.i. was obtained. This clearly indicates that an actual chemicalreduction must take place while the ingredients of the starting materialare in contact with one another in order that the novel and desirableresults of the present invention shall be attained.

While there have been disclosed herein several specific processes andcertain variants thereof, other alternatives and equivalents will occurto those skilled in the art from the foregoing disclosure. We do notwish to be limited, therefore, except by the scope of the appendedclaims, which are to be construed validly, as broadly as the state ofthe prior art permits.

What is claimed is:

1. The process of making copper-iron powder suitable for use in powdermetallurgy for forming articles having high tensile strength and highdensity, comprising the steps of introducing into a reaction zone astarting material the ingredients of which consist essentially of:metallic iron, in at least one form selected from the group consistingof (a) iron powder which has been reduced from iron oxide by a reducinggas containing a substantial amount of hydrogen chloride and (b) ironpowder which has been reduced from iron chloride by hydrogen; and ahydrogen-reducible compound of copper, in at least one form selectedfrom the group consisting of (a) the chlorides of copper, and (b) theoxides of copper; and contacting said starting material in said reactionzone and at an elevated temperature with a reducing gas containinghydrogen as its essential active reducing ingredient for a time andunder conditions sufficient to reduce the copper of saidhydrogen-reducible compound of copper to an oxidation state of zero.

2. The process according to claim 1, wherein the ironcontainingingredient of said starting material is metallic iron which was reducedfrom iron oxide by a reducing gas containing hydrogen chloride; and thecopper-containing ingredient of said starting material is copperchloride.

3. The process according to claim 1, wherein the ironcontainingingredient of said starting material is metallic iron, which was reducedfrom iron oxide by a reduc-

1. THE PROCESS OF MAKING COPPER-IRON POWDER SUITABLE FOR USE IN POWDERMETALLURGY FOR FORMING ARTICLES HAVING HIGH TENSILE STRENGTH AND HIGHDENSITY, COMPRISING THE STEPS OF INTRODUCING INTO A REACTION ZONE ASTARTING MATERIAL THE INGREDIENTS OF WHICH CONSIST ESSENTIALLY OF:METALLIC IORN, IN AT LEAST ONE FROM SELECTED FROM THE GROUP CONSISTINGOF (A) IRON POWDER WHICH HAS BEEN REDUCED FROM IRON OXIDE BY A REDUCINGGAS CONTAINING A SUBSTANTIAL AMOUNT OF HYDROGEN CHLORIDE AND (B) IRONPOWDER WHICH HAS BEEN REDUCED FROM IRON CHLORIDE BY HYDROGEN; AND AHYDROGEN-REDUCIBLE COMPOUND OF COPPER, IN AT LEAST ONE FORM SELECTEDFROM THE GROUP CONSISTING OF (A) THE CHLORIDES OF COPPER AND (B) THEOXIDES OF COPPER; AND CONTACTING SAID STARTING MATERIAL IN SAID REACTIONZONE AND AT AN ELEVATED TEMPERATURE WITH A REDUCING GAS CONTAININGHYDROGEN AS ITS ESSENTIAL ACTIVE REDUCING INGREDIENT FOR A TIME ANDUNDER CONDITIONS SUFFICIENT TO REDUCE THE COPPER OF SAIDHYDROGEN-REDUCIBLE COMPOUND OF COPPER TO AN OXIDATION STATE OF ZERO.